CA2236088A1

CA2236088A1 - Multichannel radio frequency transmission system to deliver wideband digital data into independent sectorized service areas

Info

Publication number: CA2236088A1
Application number: CA002236088A
Authority: CA
Inventors: G. William Stockton; William D. Oatman; Brent S. Simons; James H. Shoenduve
Original assignee: Individual
Current assignee: Wytec Inc
Priority date: 1995-11-13
Filing date: 1996-11-12
Publication date: 1997-05-22
Also published as: US6243427B1; JP2000500628A; EP0861559A4; DE69636836T2; DE69636836D1; WO1997018674A1; EP0861559A1; US5875396A; CN1202295A; EP0861559B1; KR19990067558A; CN1152570C

Abstract

A one-way and two-way multichannel radio frequency transmission system and method employing sectorized broadcasting and reduces the effective bandwidth of the broadcast signal by multiplexing (16) available channels of signals (14) into a set of formatted independent digital bitstreams, each bitstream including all or a portion of available channels provided by the system program provider (10). The independant bitstreams are transmitted to transmitter towers using point-to-point transmission (19) methods. The transmitting towers phase modulate (20) and amplify the bitstreams to generate a set of independent modulated signals. Each transmitter tower includes a sectorized antenna for broadcasting (41) the modulated signals to a sectorized service area at a different frequency and opposite polarity then adjacent areas, so that each service area receives a different set of independent modulated signals. Each subscriber site (49) demodulates, demulpilexes and selects one channel from the received modulated signal.

Description

W O 97/18674 PCT~US96/18804 MULTICHANNEL RADIO FREQUENCY TRANSMISSION SYSTEM TQ
DELIVER VVIDEBAND DIGITAL DATA INTO INDEPENDENT
SECTORIZED SERVICE AREAS

The present invention relates to a mlllti~h~nn~l data distribution system using radio frequency (RF) L~ ion links, and more particularly to a digitally-implemented RF iL~ ic n system for use in one-way or two-way mllltirh~nnt?l data S distribution appli~tion.~ such as video c~nre~el1ciu~g, video on ~lem~n-l, wireless cable television, and other digital data Ll~.~.c,~ n activities.

BACKGROI~I) OF THE INVENTIQN
A variety of mnl~ .",~l RF signal di~LIibuLion systems ~;ullGlllly are being employed to deliver commercial broadcast television proy,~ g to residential 10 customers. These RF tr~n~mi~sion systems often are called "wireless cable" television systems, because they can provide m~ l entertainment plo~,l,~,.l...i.~g identical to conventional cable television services, but without the cost and disruption incurred in in~lling video cable between the program provider's studio and each customer's residence.

15United States electronic e4ui~ e~l~ suppliers have m~mlf~ lred RF
Ll~n.~ x;oll systems to provide M llti~h~nn~ol Multipoint Di~Llil uLion Service (MMDS) as authorized by the United States Federal Regulations Title 47 (Telec-.""..,.ni~-~lion).
These MMDS systems have been installed in major metropolitan areas and are used by the television t;~lL~;lL~ ent industry to augment conventional television broadcasts 20 by l~ illg pl~ll,iu", videos to resi-lenti~l subscribers on a fee (pay-per-view) basis. MMDS uses allocated spectrum at various frequencies in the 2.1 to 2.7 GHz., band to Ll~u~llliL fuulL~t;ll independent channels of video. The MMDS Ll,~ , are installed at locations authorized by the United States Federal Co,-~....".ir~ti--ns ~ C~.. i~ic)n (FCC)' Each of these Ll~x.. ill~r locations has been selected so that it W O 97/18674 PCT~US96/18804 can broadcast into the surrounding service area without clcaLulg illLelrel~llce in the adjacent service areas.

In responding to the need for AAf7itinnAl wireless multipoint television di~l~ibulion ~e.,L,ulll (i.e. in addition to the authorized MMDS spectrum), the FCC
issued an interim operating license in the 27.5 to 29.5 GHz band. The trrhnn1~7gy employed for use of this spec;llulll has been ~7,esi~nAtP~ Local Multipoint Di~ uLion Service (LMDS) and one implementation of a LMDS is disclosed in U.S. Patent Application Serial No. 4, 747, 160. Both LMDS and its predecessor MMDS
broadcast mnltirhAnnPl television signals into specified "service areas". Service areas (also referred to as "cells") identify non-~vel1~3pillg geographic regions that receive hl~el~lellce-free tr~7nxmicsi~n from sepdldl~ sites.

Another prior art television broadcast technology similar to LMDS is c7esignAtPd l~illimPtf-r-wave M-ll~ nl~rl Multipoint Video Dislli~uLion Service (M3VDS) and is described in detail in 1989 IEFE MTT (pages 1095-1102).

RerAll~e all of these systems have similar con~igurations and because they employ related technologies, it is useful to regard these wireless mllitirh 7nnf~1 television RF broadcast systems as impl~ ions of the same system concept.
Henceforth, these systems (i.e. MMDS, LMDS, M3VDS, and any si nilar system) willbe referred to as multipoint distribution systems (MDS).

Referring to Figure 1, an MDS typically includes a program provider site 10, a plurality of service area broadcast trAnxmittPr towers 11, and a plurality of subs~li7.,t;l~ 12 in each service area. The program provider di~lli7.ut~s multiple rh-7nnPlx of signals (via satellite, cable, point-to-point ~ ;l ow~ve l, A ~lx~ . ~ixsif~n, or fiber optics or any other LIAn~ ixxif~n mPr.7inm) to each of the service area 11An~
towers. Each tower, in turn, bro~flrA~tx via RF IlAnx...iSxion the l~ceived signals ~., (cf)mm- nly analog signals) to a plurality of subscribers residing in the vicinity ~u~ undh~g each given tower (i.e., the service area). The range of signal trAnxmixsif)77 for a given tower (and con~e.luen~ly the size of the service area) is WO 97/18674 PCT~US96/18804 primarily dependent on the power ch acleli~Lics of the signal being L~A~ by the given tower. Each subscriber within a given service area uses an antenna and receiver unit coupled to a television to receive and view the television signals broadcast from the IlAI~Inill~l tower within the given service area. Selection of the desired television 5 channel and ~ of the audio and video parameters is pelrolllled at the television set in the subscriber site by means of controls located on the television or by a remote control unit.

Presently, MDS systems L~ slniL multiple channels of television signals from the service area broadcast towers in parallel. In other words, each distinct television 10 channel (having a given modulation bandwidth) is individually and .cimllltAntoously L1AI~;III;II~(1 Thus, the total bandwidth of the broadcast signal is equal to the sum of the modulation bandwidths of each of these channels plus any additional spectrum used as spacing between the channels to Illi~ e mutual illL~lr~lence.

As an example of this spectrum utili7Ation, MMDS television broadcast 15 systems in the United States employ amplitude modulation (AM) methods which require 6 MHz of bandwidth for each television channel. Up to fourteen of these 6 MHz chAnnl?le are broadcast by MMDS systems. In contrast, LMDS television broadcast ~7y~ llls in the United States ~;ullelllly employ frequency modulation (FM) methods which require 20 MHz of bandwidth for each television channel. The 20 LMDS system employs l GHz of spectrum which enables it to broadcast up to fifty of the 20 MHz wide chAnn~le. In the United King~lnm, the M3VDS television broadcast system employs FM m.othorls which require 38 MHz of bandwidth for eachchannel. C~oneeql7ently, the M3VDS system required 304 MHz of spectrum to broadcast the eight television ~hAnnPIe initially specified by the British television 25 broadcast authorities.

The m~ lAtion methods employed in the above prior art MDS systems c~-mple~ly consume the available spec~ lll while broA~rAefin~ collv~ ional television ~ progiA~ g. However, the current trend in cable television technology is to irLstall additional rh~nnf~le So that special video can be provided to hlL~resl~d subscribers.

W O 97/18674 PCT~US96/18804 Potentially, these ~ litinn~1 ch~nn~ls would be used in special applications such as video-on-d~m~n~l and video conrclcllcillg for selected subscribers. In addition,these rh~nn~ls might be used for co~ u~cl and data retrieval tasks, for access to the Internet and other data bases, and for illLc,a;~ive applications such as video games and home 5 shopping. These special applications which are targeted at individual subscribers are ~om~timrs ~efiignz~t~d "l~luw-,asts" to dirrelc,~Liate them from the usual e~lL~lL;~
television progr~mminp~ that is "broadcast" to all subscribers. Ndllov~ a~L~g requires many individual and independent ch~nnt?lx so that many individual subscribers can be served siml1lt~n~ously.

Another drawback of presently imp1emlo-ntPd MDS systems results from signal iulLcld;lion bclwcell adjacent service areas. Specifically, subscribers in vicinities residing along the boundary of a service area may receive signals from the desired service area Ll;l-lx-~ -l tower and also from one or more adJacent service area tr~nxmitt~-r towers. These multiple signals entering the subscriber lcceivel e4ui~ ent 15 often result in ~i~..ir.~ l degradation of the desired signal quality. Thus, one important design consideration of an MDS Ll~nxlllixsion system is to ensure that each subscriber receives a strong illlelrelellce-free signal.

One prior art MDS system desi~nr~l to avoid mutual illle,rt;lel~ce problems among ~ ce~t service areas ~disclosed in US Patent No. 4,747,160) employs omni-20 directional polarized antennas, each antenna bro~1r~ctin~ into a circular service area.
Each antenna L.al~llliLx signals having either a horizontal or vertical polarity.
Subscribers in this prior art system use directional antennas that are tuned to a given xlllix~ n polarity and physically aimed towards a ll;-llxlllillP.i tower having the corresponding polarity. As a result, illltlre:rence from an adjacent Ll,.~ el- tower 25 is elimin~tlo(l if the ~ rent tower is tr~nxmitting a cross-polarized signal. However, the problem with this ~dllslllission scheme is that only two polarizations are available, but there exist some subscriber locations which will be i11...~i..;.l~cl by Ll,~ .xions from three or more towers. At least one of these additional illLtlrt;~illg signals will be of the same polarity as the xul~s~lil)el~s antenna. Consequently, at least one 30 inLt;lr~ g signal may enter the subscriber's antenna along with the desired signal, and WO 97/18674 PCT~US96/18804 the quality of the desired signal may be degraded substantially.

The present invention is a digitally implPmP-ntlocl multichannel data distribution system and method that overcomes the above described problems. Specifically, thesystem of the present invention employs digital signal ~loces~ g techniques to S combine the analog television channel signals (i.e., the audio and video signal components) and other channel signal types (such as digital television signals, teleco~ e~ g signals, interactive pro~ ;..g signals, CO111~UI~;1 data signals, and video-on-demand signals) into a single stream of r~ " ~ r~l data. Then, the system of the present invention uses special m~lnl~tion mPtho-ls to reduce the effective spectrum 10 bandwidth of the ll~ d signal. As a result, the present invention is able to fit many more independent channels into an authorized operating spectrum bandwidth than can the prior art L~ x.llixxil-n systems thereby overcoming the prior art limit~tion of obtaining many individual and independent ~h~nnPls required to implement .-al 1 ow~;asting .

The system and method of the present invention also employs a mnltif~ecl sectorized antenna at each of the Ll~nx~ sites 11. The sec;l~ ed antenna, c~,l"~>,ised of a plurality of independent smaller antennas, essentially divides each service area into a plurality of independent wedge-shaped ~7imnth~1 sectors. For each ~7imnth~1 sector, independent channel signals and other data are received from the 20 provider studio as a single digital data stream which is mo~ tP(l, amplified, and tr~nxmittPfl to the ~pl~iate subscribers residing in that specific sector. The signals ~ n~ d into the other ~7imllth~1 sectors surronn~ling the L~ xll.ill~-l site areindependent of one another and contain different data that is of interest to thesubscLil)el~. in those other sectors. Furthermore, the antenna polarities of ~ rPnt~5 sectors are of opposite polarities. Thelefo~e, the RF signals from the two sector x cannot combine destructively, and the subscriber ~ntPnn~ will receive only one of the two possible sector signals.
.

~ The current invention can be imp!empntpd either to provide only o ne-way wideband tr~nemieeion from the provider site through the lli.n~;lllill~l sites to W O 97/18674 . PCT~US96/1880 the subscriber sites, or it can be im- plçment~d to provide two-way wideband LlAne.~ ns between the provider site and the subscriber sites via the ~lAI~ r sites.

In the ~lcf~lcd embodiment, the two-way wideband LlA~ ision process S would be used for video collr~encillg between subsclil)~l~. Consequently, the provider site would not be the final dçstin~ti-)~ for the L~ "~ixeion from the subsclil)els, but it would provide ~wik;llhlg service to intercormect the two-way LIA~el..i~ions among the :,ubs(;libels who are pdl~icip~ lg in the video col~lcllce.
AlLclllalively, the ~wiLI_llillg filnrffnn could also be provided at each tr~n.emi~si~-n 10 tower, thereby eli~ AIillg the need to route all signals back to the provider site.

The present invention is a digitally-implPmPnt~cl mllltirh~nn~l data distribution system and method using a sectorized RF L~anslllission t~rhniqlle The invention can be implem~nt~d as a one-way signal LlA~.e~ sion system or as a two-way signal 15 trAn~mi~si-~n system.

The one-way system of the present invention includes three subsystems; the provider site, the trAn~mittpr site, and the subscriber site.

Examples of channel signals that can be L-AI-~ d by the system of the present invention include analog television signals (i.e., analog audio and video 20 signals), follll~llcd digital television signals, telecollrt;rcnciLIg signals, illL~l_LLivc pro~lA--,---i-lg signals, colll~ulcl system data signals, and video-on-demand signals.
Each of these rh~nnPI~ may be provided to the system in a dirrelcn~ format, depending on the inform~tion being LIAn~ d within the channel. In some cases channels are initially pre-con-liti--nPd by the program provider of the present invention in order to 25 facilitate subsequent processing steps. All analog signals need to be converted to a digital form and, if n~cç~ry, the digital data rate must be colll~lessed. In oneembodiment, analog television channel signals are analog-to-digital (A/D) converted and compressed using MPEG ~nd~d data compression f~.ll~uillg. In other W O 97/18674 PCTrUS96/18804 emborliment~, other co~ ,ssion techniques and formats can be used.

Once precon-liti.~n~r17 the channels to be ~lA~ d into the service sector aremultiplexed together to forrn a single strearn of interleaved digital bits ~ esell~ing all of the channels. In the pleÇelled embo.lin~ont this multiplexing step is achieved by 5 time division multiplexing. In another embo~lim~nt multiplexing is achieved byfrequency division multiplexing The digital stream of bits is then formatted into a frame format so that the channel information within the bit stream is distinguishable when pelrulnli~lg subsequent signal processing steps. In one embodiment of the present invention, SONET STS-3 frame fo,l"auiLlg is ~ltili7~f1 To serve each of the sectors in each of the 1~ l sites, the provider site creates eight independent bi~ llS for each IlAn~ site, ~suming that the site employs eight sectors in its service area. In one embodiment of the present invention there is a one-to-one correspondence between the number of sectors and the number of independent bi~~ ~lls created by the provider site. In another15 embodiment, some of the sectors share the same independent bii~ S.

Once the channel signals are converted to a digital format, a single bi~LIe~
is formed by interleaving each of the channels together in a process known as time division multiplexing (TDM).

In the p~erelled emboflim.ont the time division multiplexing process is 20 accomplished by first '~p~ ti7ing~ each digital channel into A~yll(;hl-ollous Transfer Mode (ATM) packets. Pack~ti7ing a bi~lle~ull into ATM packets or ATM cells involves dividing the biL~LIedlll into 48-byte segments and adding a 5-byte header to form a single ATM cell.

The ~l~relled embodiment time-interleaves the ATM cells from each of the 25 digital channel sources into a single, high data rate biL~lle~lu In turn, this single - biL~Ie~ll is further Çul.llA~ d into Syncllronous Optical NETwork (SONET) or Syllchlollous Digital Hierarchy (SDH) frames. The result is a signal that can be -W O 97/18674 PCT~US96/18804 di~LIilJul~d from the provider site to cle~ign~t~d ll~n~ sites using well known techniqnes such as mi~,uw~ve point-to-point radio systems, relay via satellite, l over optical fiber lines, or any other similar L~ n method.

In another embo~lim~nt the channel signals are multiplexed by frequency 5 division multiplexing. In this type of system, each channel signal is modulated onto a dirr~lcl~l carrier frequency. The carrier frequencies are selectec~ so that each signal is undistorted by the ~l~,s~l~ce of other signals. All of the unique, mc ~1nlAtl?(l carriers are then sllmm~d together to form a single signal which can be distributed from the provider site to cle~ign~t~i trAn~mitt~r sites using the techniques described in the 10 previous paragraph.

A 1~ site puts the in-~nming digital data streams from the provider site into condition for trAn~mi~ n via RF means to the subsclibe, sites. For each of the incoming dat~ streams, the LIAI~ site modnlAtlos the bi~L~ l onto an i.ll~.lll,ofli~t~ frequency (IF) carrier. In the prer~.led embodiment of the present 15 invention, four phase mo~lnl~ti--n is used. In other embo~lim~nt~ of the present invention, eight-phase or frequency shift mo~lnlAti--n may be employed. In one embo-lim~nt. the Square Root Staggered Quadriture Phase Shift Keyed ~SQR-SQSPK) modulation format of the present invention is employed. The SQR-SQSPK folmat mn~ tion technique is a phase modulation L~clmi~ue that restricts phase changes to -20 4~, 0, and +45-. This phase step restriction reduces amplitude variations in the mor~ t.orl signal due to large phase transitions ( > 45 ~ ) when l~hAnging from one logic state to another. This moclnl~tit~n t~hniqll~ is implem~ntlo~l by mapping the digital l)il~LIe~ll into an intermediate bi~LI~,A ll that when mo~nlAt~l by a standard eight phase modulation technique generates the SQR-SQSPK r~"~ ~d signal of the present 25 invention.

After mo~llll~tion, each of the independent IF signals are frequency shifted (i.e., upconverted) to one of a set of predetermined radio frequencies (RF) within the pre~esi~n~te~l ~ecLl ulll range such that adjacent Ll A ~ er sites employ different RFs to avoid i~ rt;lhlg with one another's signal L~A.~ ions. In one embodiment, W O 97/18674 PCTrUS96/18804 signals are upconverted to one of seven RFs. In another embodiment of the present invention, the signals are upconverted to one of four RFs. After upconversion, each of the independent RF signals are c~nn~ctPd to the ap ~ proplid~ sector L~ Pl antenna in the present invention and radiated out to the 5 subscriber sites in the sector service area.

In the IJlcr~ d embor1im~nt of the present invention a semi-on-luçtor RF
amplifier followed by a non-linear diode frequency doubler is employed to produce the required output power and to obtain the long o~eldl-~lg lire~.~dl~s CO1LSi~ with economical operation. A second embodiment of the current invention uses 10 semiconductor RF generators and sdluldling amplifiers to geneld~ ~-ieqll~te output power with long opeldLillg lifespans. A third embodiment of the current invention makes use of linear RF semiconductor devices for low power, short range data n applications. The embotlim.onti of this invention which employ the non-linear device and the saturating amplifier device require waverolllls with phase or 15 frequency modulation that have constant amplitudes. However, the embodiment employing the linear device can make use of phase, frequency, and amplitude modulation formats. The modulation format of the embodiment of the present invention that uses a non-linear amplifiers device is the SQR-SQPSK mc-llll~tionformat of the present invention.

The antenna of the present invention is a mn1tif:~e~1 polygonal-shaped cylinder,horn or disk, where each of the faces of the cylinder constitute one distinct sector :~nt~nn~ Each sector antenna lla~.llliL~. an independent signal into one of a plurality of wedge-shaped sectors within a given service area. In one embodiment of the present invention, an eight-faced cylinder is employed. In other embo~lim~nt~, any even number of antenna faces can be used.

In a variation of the above embodiment, only a portion of the sector all~mlas are used. This embodiment is useful when the ll~ site is located near a large ~ obstruction, such as a mountain, and the system does not need to ~ .llliL signals into the sectors which contain the obstruction. In this case, the likelihood of hll~lr~lcllce occurring in the other sectors due to signal reflectinne from the obstruction is reduced.

Subscriber sites each include an anterma for i~eiving the L~ d signal each being designP-l to receive signals having a particular polarity. Subscriber sites also include a d~mod~ ~r for demcdnl~ting the ~ d signal and a demultiplexer S for il~ Lillg and sel~ctin~ one of the multiplexed channels co~t~inP<l in the signal received from the Ll~ rL site. The d~mllltiI lexer is controlled by a subscribercontrol unit, commonly a remote charmel selector device.

The selrct~ d channel provided by the dem--ltil-lexer is electrically routed to an external device depending on the illrollllaLion signal co~t~inPd in the channel. For 10 i~ re, a television channel is routed to a television, and a collll~uL~I system digital data signal, such as an INTERNET signal, is routed to a C~ uLel system. In oneembo-lim~nt ch~nnr1e (such as television ch~nnP-le) that were initially A/D converted and coll~ ssed at the program provider site are l~cullvc~lL~d back into their original forms before being routed to the final output device.

The two-way implel . ,~ l inn of the present invention allows for two-way wide bandwidth Ll~n~.iexions bGIwc;en the provider site and the subscriber sites. The signal path from the subscriber to the provider site (referred to as the b~c~ l) is a wireless data link L~ rcl through the subscriber's ~nt~nn~ at a nnmin~l carrier frequency other than the operating frequencies used for bro:~-lc~eting signals from the 20 Ll~ "~ Pr sites to the subscriber site. The data cnnt:3inPd in the barl~ch~nnrl can be Pay-Per-View request data, video images for video-collr~ iillg or ~ t~nre learning, or several other digital data streams which one may wish to use the wireless link to connect with other public or private networks.

In the case in which the two-way wide bandwidth Llal~lllis~ion process is used 25 for video conferencing beLwe~n subscl ib~l s, the provider site is not the final in~ti/~n for the ~ ",ieeion from the subs~ . Tnetra(l, it provides ~wiL~;hiug service to interconnect the two-way Lli.n~ ie~inne among the ~,lbsclil)el~ who are pallici~dLillg in the video co~ el,ce.

W O 97/18674 PCTAUSg6/18804 BRIEF DESCRIPTION OF TE~E DRAVVINGS
Figure 1 illustrates an example of a local mllltirh~nn~l di~llibuLion system (LMDS) including a program provider site, a cell Ll,~l~cllli~ site, and a subscriber site.

S Figure 2 is a block diagram illustrating one embodiment of the one-way implt;~ LaLion of the system and method of the present invention.

Figure 3 illustrates one embodiment of the provider ~ul~y~ of the present invention in~ ling the Video Encoder Segm~ont of the present invention and the Signal Multiplexer Segment of the present invention.

Figure 4A illustrates a b~n~llimit.od conventional staggered QPSK follll~lL~d signal.

Figure 4B illustrates the b~nf11imitPd square root staggered QPSK (SQR-SQPSK) f~JlmdlLt;d signal of the present invention.

Figure SA shows one embodiment of an IF Modulator Segment of the present 15 invention.
Figure 5B illusLldL~s a phase state look-up table used to l~elrollll the SQR-SQPSK modulation t~rhni~e of the present invention.

F;gure 5C illustrates the constellation diagram corresponding to the look-up table shown in Figure SB.

Figure 6 illustrates one embodiment of a RF Power Segment of the present illv~ ioll which employs a non-linear saturating amplifier and diode doubler power amplifier.

Figure 7 is a graph illustrating the manner in which RF signals are broadcast at dirr~ operating frequencies to dirr~lcllL service areas in accordance with the CA 02236088 l998-04-29 ~ ~ ¦U S 9 6 / 1 8 8 0 4 IPE~/llS 13 .~UN 1997 method of the present invention.

Figures 8A-8D illustrate graphical chara~;leLiGaLions of a conventional staggered QPSK formatted signal before and after b~n(llimiting and amplifying.

Figures 9A-9D illustrate graphical chara~;Lel iGaLions of the SQR-SQPSK
S formatted signal of the present invention before and after b:ln~llimiting and amplifying.

Figure lOA illustrates an overhead view of one embodiment of the antenna of ~' the present invention implemented with eight antenna panels.
Figure 10B illustrates an overhead view of one embodiment of the antenna of the present invention implemented with six antenna panels.
Figure 11 illustrates an array of tr~n~mitting sites in accordance with the sectorized tr~n.~mi~sion method of the present invention.

Figure 12A illustrates one implementation of the RF Demodulator Segment of the present invention.

Figure 12B illustrates one implementation of the Settop Box Segment of the 15 present invention.

Figure 13 illustrates an example of spectrum allocation for the forward channel and backch~nn.ol bands in a given sector in accordance a two-way embodiment of the present invention.
D ET ArLED DESCEU~YrIO N
The present invention is a digital mllltirh~nn~l RF Ll~n~ ion system and method. In the following description, numerous specific details are set forth, such as operating frequency and frequency spectra, in order to provide a thorough understanding of the present invention. It will be appalcnt, however, to one skilled in the art that these specific details need not be employed to practice the present 25 invention. In other instances, well-known signal processing structures and steps have not been described in detail in order to avoid nnn~ces~rily obscuring the present ~ SHEEr invention.

The digital mlllSirhAnn~l IlAn!~",ie~ n system of the present invention is a method and system that reduces the effective bandwidth of the broadcast signal by multiplexing selected channel signals into single digital biL~Lleallls. Reducing the S bandwidth of the broadcast signal gives program providers the flexibility to provide lifionAl channels within the broadcast ~e~;Llulll. In ~d-litic n, the system and method of the present invention employs a sectori_ed bro~lr~eting t~chni~ e that esse~ti~lly divides service areas into a plurality of sectors, each sector lt;ceivillg an independent broadcast signal and adjacent sector antenna's ~ g opposite polarity signals.
10 This broadcast technique allows for a broadcast system that can be customi7P(1 to the specific needs of the subscriber within each sector. Furthermore, due to the reduction in bandwidth of the broadcast signal, each service area may be ~1esign~d to broadcast at one of a set of operating frequencies within a given spectrum, thereby reducing illlt;lÇ~,ence between service areas.

The mllllirhA,----~l di~L il~uLion system of the present invention includes three sub-systems as shown in Figure 2: program provider subsystem 10, Lli1n~ rL
~ub~y~L~lll 11, and receiver subsystem 12.

Provider sub~y~ ll 10, including the Video Encoder Segment 13 and the Signal Multiplexer Segment 16, performs the steps that reduce the input channel 20 signals 14A and 14B into sets of single independent biL~LIe~lls 19. Provider sub~y~L~lll 10 leceiv~s many types of channel signals including: 1) analog signals 14A, such as analog TV signals which are often in a standard PAL or NTSC analog format and 2) digital signals 14B, such as digital TV signals, which are already fi~rmAtt~i into a standard digital format, and other digital data signals such INTERNET data, video 25 col~ ellcillg digital signals, etc.

Video encoder segment 13 collvelL~ all analog signals 14A into digital signals - and then further converts these signals into a pred~Lt;llllilled digital c~ ssion format. Conl~l~ssillg the A/D converted television signal reduces the bit rate of the digital television signal to facilitate subsequent processing. Figure 3 illustrates one embodiment of a Video Encoder Segment in accordance with the system of the present invention. In this embodiment, MPEG Video Compression Encoders 15 are used to compress rligiti7~:d PAL- or NTSC-formatted analog TV signals 14A into MPEG-5 compressed digital signals 14A'. However, other digital colllplession formats can beemployed to encode analog signals 14A and analog signals 14A may be in a format other than the PAL- or NTSC-format.

It should be noted that other channel signals may be processed dirr~lcl~Lly. Forin~t~n~e, if the provider ~ulJsy~t~lll 10 l~,cei~es a digital channel signal that is already 10 in a compressed format, then no conversion is required. As shown in Figure 2, digital signals 14B are passed directly to signal multiplexer segm~-nt 16 without p~,lrOlll~illg any collvel~ion steps.

In Figure 3, up to m analog video signals plus x digital bi~LL~ulls are shown as inputs into the Signal Multiplexer Segment 16. The total number of independent 15 and unique ch~nn~ls consisting of analog video and digital bil~ ,dlllSiS n..
The Signal Multiplexer Segment 16 controls how the channel signals 14A and 14B will be multiplexed into the single output bil~ ;~ll 19. Each of Signal Multiplexer Segmtont~ 16 gene,al~;s an independent biL~L-e~ll 19 C~Jllll,lisillg all or a portion of channel signals 14A' and 14B. Thus, each of in~l~penr~ont bikiLIe~lls 19 20 shown in Figure 2 may comprise a dirr~ell~ set of channels. The number of biL~ lls 19 is dependent on the number of antenna panels that the ~nt~nn~ of thepresent invention includes. For example in the embodiment of the present invention that employs an antenna having eight antenna panels, eight independent bil~ allls 19 are gellt;ldL~d for each ~ c~ r subsystem 11. This allows a dirr~rell~ signal to be 25 coupled to and broadcast from each of eight antenna panels in a given service area.

Figure 3 illustrates one impl~ lion of the Signal Multiplex Segm~nt 16 of the present invention. In this impl~",~l.l;,linn, Signal Multiplexer Segment 16 processes each of the digital dal~ ealll channel signals (n channels total) from the W O 97/18674 PCTrUS96/18804 various sources through an Error Correction Encoder 17A. The number of digital datastream channels (n) is an impltll.e.lLdlion choice dependent upon the type and bit rate of the daLd~Lle~lls to be supported and the quality- of service required by each channel. The Error Correction Encoder 17A allows each channel to be individually5 opLil--~ed for error detection/correction performance while ope~aLi~lg within the system. Signals requiring very high fidelity and low Bit Error Rates (BER), such as MPEG-encoded digital video signals~ are encoded with higher pelf~llllallce (and greater overhead) error correction codes than signals which do not require the same lBER pe~r~ ce for acceptable operation.

Following the Error Correction Encoder 17A is the Timebase Corrector 17B.
The Timebase C~ ,elor 17B ~y~chrol~es each channel signal's bit rate to a cornmon clock source. Thus, all samples will be lefel~nced to a single clock at the provider sub~y~Lel.. 10.
.

Time division multiplexer 18 (Figure 3) interleaves channel signals #1 through 15 #n into a single high speed biL~le~ll 19. In one embodiment, each charmel signal is first packetized into an A~yll~l~ollous Transfer Mode (ATM) packet (or ATM "cell").
The p~c~ti7ing process collects the channel daLasLleall~ into 48-byte segments (each byte equals 8-bits) and adds an additional 5-bytes of header information. This is called an ATM packet or ATM cell. The ATM cells for a specific channel are then 20 illlelledved together with other channel ATM cells and with "framing" illfulllldlion.
Framing illf.,llllaLion consists of a repetitive interleave pattern and additional information within a specific time sequence (also referred to as a frame). This additional ÇolllldlLillg is n~cç~ y in order to ensure that each of selected channel signals #l through #n multiplexed within bitstream 19 is rli~tin~li~h~hle within the 25 biL~Lle~ll. The fo....;.lli.lg step pelrolllled by multiplexer 18 inserts additional control, error and timing illr~ lld~ion bits to generate formatted bit stream signal 19. The additional folllld~ g bits primarily function to indicate the start of the bit frame and to keep track of the location of channel signals #l through #n within the bit frame so - that these signals remain i-l~ntifi~ble in suhsequ~nt processing steps. In one 30 embodiment of the present invention, SONET STS-3c bit fraTne r ,....~ll;..g is WO 97/18674 PCT~US96/18804 pelr~.lllled by multiplexer 18. However, it is to be understood that any similarformAtting technique can be employed.

The advantage of the present illvellLi~n as compared to the prior art Ll~n~"~i~einn systems is that the prior art Lldl~llliLs mn~ t.od rh~nn.ols in parallel -5 each channel using a portion of the allotted LMDS s~e.;L.ulll. In contrast, the presentinvention multiplexes selectf-d channels into a single biL~llc~ull 19 which is then digitally modulated with a bandwidth-errlciellL modlllAtion tochniq~e which reduces the effective bandwidth of the broadcast signals. For instance, one prior art LlA,~c",ie~;inn system uses up to 1 GHz of the LMDS spe~Llulll to l~ up to 50 channels (each10 approximately 20 MEIz wide) by l.~ g mndlllAt~d analog signals in parallel.
The present invention, on the other hand, multiplexes up to 81 television channels into a single biL~ ll broadcast single having a bandwidth that is ~ ly equal to80 MHz thereby using a ~i~l,irir~,lly smaller portion of the LMDS ~l e-;l, Ulll than the prior art method. One advantage of this reduced spectrum usage is that the present 15 invention is able to fit more channels within the LMDS ~ecl~u-n than the prior art method. Thus, where prior art methods might have to give up a portion of 50 channels to make room in the spectrum for other charmel types, such as an INTERNET channel, the present invention can fit the standard ch~nnPls and still have enough ~ecLlulll left to provide for other charnel types.

In order to Lldl~llliL biL~Ll~ullS 19 the signals must be put in suitable condition in accordance with the trAn~mi~ion method used to llal~lllil the biL~LIealll(s) between provider sub~y~lt;lll 10 and LIA~ I"il~ iUlJ~y~iLt~ . Several different point-to-point digital LlA"~ n methodologies can be used such as satellite, cable, point-to-point microwave IlA..~ ion, or fiber optics. The particular processing steps performed25 to put the biL~L~ l(s) in condition for trAn~miq~inn is dependent on the L~A~ inn methodology used and should be ~,vell understood by one skilled in the field of co""".ll.i~linn systems.

TlA"~",;Il~r sul~y~ lll 11 connects an IF Modulator Segm~nt 20 to each of independent and unique biL~Li~s 19 and generates a mn~lnl~t~-l signal centered at an WO 97/18674 PCT~US96/18804 intermediate frequency (IF). RF Power Segments 21 frequency shifts the modulatedsignals from the lF frequency to the final broadcast opeldlillg frequency and provides the nPcess~ry amplification for wireless tr~n~mi~ n to the lcceivcl sub~y~Lclll.
Modulator Segment 20 and Power Segment 21 (Figure 2) can be implemented in many different lllal~nel~. For in~t~n~e, in a first embodiment of the presentinvention bil~llt;allls 19 are mo~ t~d into either an amplitude, phase, or frequency formatted signal at an intermediate frequency (IF) less than the broadcast radiofrequency, tr~n~l~tçd in frequency to the ~mal broadcast operating frequency, and then amplified with linear power amplifiers adjusted to operate at the final broadcast 10 frequency. In this embodiment, it is ~-~cçq~y to use linear amplifiers since a non-linear amplifier does not produce the desired modulated signal when amplifying am~ tP~l signal having amplitude variations (such as an AM signal). Cullclllly, linear power amplifiers m~mlf~rtl~red to amplify relatively high radio frequency signals are considered to be an expensive but unavoidable device implp~llp~ n choice.
15 Consequently, although this embodiment is able to produce a broadcast signal having the desired modulation and power cllAld~ istics, the overall cost of a system implemented in this manner is greatly increased due to the nPcçcqity of using linear amplifiers.

In a second embodiment of the present invention, biL~lie~lls 19 are mo~1nl~t~ c~20 using a constant amplitude modulation format (i.e. either phase or frequency mo~ tic)n), mixed to the broadcast RF and then amplified using conve ntional non-linear amplifiers. Although this embodiment provides the desired modulated signals, and avoids employing linear amplifiers, some illac~;ulacies may occur when amplifying the phase or frequency mo-llll~t~l signals with the non-linear 25 amplifier. Specifically, although phase and frequency modulation does not useamplitude variations to encode logic state changes, amplitude variations still do occur when rll~"~ logic states. Non-linear amplifiers do not tolerate amplitude variations and as a result, may provide erroneous output signals due to these amplitude - variations. Furthermore, ~,ullCllLly available high frequency non-linear amplifiers on 30 the market tend to provide a limited amount of power thereby Illillillli~illg the available W O 97/18674 PCTrUS96/18804 bro~lr~ting power.

In a third embodiment of the present invention, biL~LIc~lls 19 are phase modulated into the Square Root Staggered Quadrature Phase Shift Keyed (SQR-SQPSK~ modulation format according to the present invention. The SQR-SQPSK
5 format of the present invention is obtained by performing a standard 8-phase modulation with the added restriction that phase ~h~n~s of only +45-, O-, and -45 can occur at each clock period so that amplitude variations are reduced (co~ ed to a conventional staggered QPSK(SQPSK~ signal) when tr~n~iti--ning from one logic state to another. The SQR-SQPSK formatis also chalaclel.,ed such that when 10 amplified by a doubler power amplifier it generates a conventional SQPSK signal; (it should be well known in the field of cl.l.l.~.. if~ti~-n system design that a doubler power amplif1er functions to double the frequency excursion or the phase excursion of a signal).

The SQR-SQPSK is a modulation format that is specifically rl~ci~nPd to 15 generate a signal that is to be amplified with a non-linear saturating amplifier or an amplifier with a doubler. These amplifiers provide adequate power using solid state devices. Furtherrnore, due to the SQR-SQPSK modulated signal's constant amplitude, it is ideal for saLulaLillg and non-linear amplifiers because amplitude variations produce distortion in the output signal.

Figures 4A and 4B illustrate the amplitude time histories of a conventional ban~llimh~-l staggered QPSK signal and the SQR-SQPSK r~.. ,.llrd signal of the present invention, ~ ,pe.;Lively, each being generated by mc~ ting the same input signal. As can be seen, the conventional SQPSK signal has much larger amplitude variations vs. time c~ al~d to ~e SQR-SQPSK formatted signal of the present 25 invention. Hence, amplitude variations are reduced in ~is phase m-)cllllzltic n technique such that a saluldLil~g non-linear amplifier can be ~rr~ ively employed.
In the embodiment of the system and method of the present invention using the SQR-SQPSK modulation format, biL~L.Ga-lls 19 are first mo~ t~(l into SQR-SQPSK
follllaLL~d signals onto a first IF carrier. The modulated signals are then mixed to a W O 97/18674 PCT~US96/18804 second IF ~equal to half t~e desired broadcast RE;~ and amplified with a non-linear amplifier tuned to the second IF frequency. Finally, the amplified signals are frequency doubled to the desired broadcast RF by a doubler power amplifier to obtain conventional staggered QPSK signals at the desired broadcast RF.

This embodiment of the present invention is superior and more economical than prior art embodim~ntx that use high frequency linear and non-linear amplification techniques since the present invention's technique initially amplifies at a lower IF
frequency (i.e. half the broadcast frequency) using a non-linear amplifier and then doubles the frequency using a doubling power amplifier. By amplifying a SQR-SQPSK formatted signal with a non-linear power amplifier tuned to a lower frequency and then amplifying again with a doubler power amplifier, the L~ x~ rr subsystem11 of the present invention can be implem~nt~d more econnmi~lly than prior art Ll,-llx--lillrl ~,ulJsy~L~;lllS.

Figure 5A shows one embodiment of an IF Modulator Segment used to generate a modulated signal having the SQR-SQPSK format of the present invention.
Each IF Modulator Segment 20 receives one of the independent biLxLIe~lls 19. Thedata and clock recovery unit 22 derives the original signal 19 and an associated clock signal which is used in subsequent modulation processing steps. Bitstream signal l9 and its associated derived clock signal are connected to a Serial-to-Parallel Converter 23. The Seria1-to-Parallel COllv~lLe~l 23 formats the serial data into two-bit words, which l~LestllL the Present Phase State 24A of the present data word. The Present Phase State 24A col~ h~ed with the Past Phase State 24B generate an address into the Phase State Lookup Table 25. The output from the Phase State Lookup Table 25 is a three-bit Phase Data Word 26. Two clock outputs are also generated in the Phase State Lookup Table 25. One clock is a divide-by-2 version of the clock input into the Phase State Lookup Table 25 (denoted as CLK/2) and the second clock is an inverted version of the divide-by-2 clock (denoted as CLKt2').

The three-bit Phase Data Word 26 is routed to an I Lookup Table 27, a Q
Lookup Tab}e, and a delay element. The delay element routes the Phase Data Word CA 02236088 l998-04-29 26 output back into the input as the Past Phase State 24B.

One embodiment of the present invention uses an eight phase modulation technique to ge~ aLe the SQR-SQPSK signal. A constellation diagram showing the possible phase states in shown in Figure SB, and the Phase State Lookup Table 25 is 5 shown in Figure 5C. In the diagram, each possible three-bit output word from the Phase State Lookup Table is mapped into a cu-lcspol~ding point in the constellation.
Note that Phase State Lookup Table 25 lc~SLli~;L~ phase rh~n~s to +45-, 0', and -45' from one logic state to another.

The I Lookup Table 27 translates the 3-bit phase data into a corresponding 10 digital word suitable for the I-data Digital-to-Analog G~ velLt;l 28. The Q Lookup Table functions in the same manner for the Q-data Digital-to-Analog C~llvelLel.

The output from the I-channel and Q-channel Digital-to-Analog Collvt;lLel~ are routed to Shaping Filters 29. The outputs for the Shaping Filter 29 are conn~ct~l to the Quadrature Modulator 30A, where the baseband analog data is modulated at carrier 15 frequency supplied by the 1st LO Source 30B. The output from the Quadrature Modulator 30A is the Modulated IF Signal 31.

Figure 6 show one embodiment of the RF Power Segment (21). The IF
Modulated Signal 31 is filtered by R~n-lr~c~ Filter 32 to filter out signals at frequencies other than the mo~ ti~m carrier frequency. Next the filtered signal is 20 amplified by Amplifier 33, and then frequency shifted by Mixer 34 to one of a set of opeldLil~g frequencies. The 2nd LO Source 35 is the frequency source that ~lPL~ PS
the final carrier frequency out of the RF Power Segment 21.

All sectors within a given service area are broadcast at the same o~ LLillg frequency and adjacent Ll,. ~ subsystems broadcast at dirrt;ielll operating25 frequen-~içs . In this way subscribers in a first service area do not e~el it;nce illL~IÇele~lce from signals that are being broadcast in ~uil~Junding service areas. The dirr~ opcldLillgfreq i~n~ betweendirr~iellLLI~ .. subsy~L~ broadcastareas WO 97/18674 PCT~US96/18804 are determined by selecting a different 2nd LO Source 35 center frequency setting.

An example of how signals for each service area are frequency shifted is shown in Figure 7. In this example, the n modulated signals being broadcast intofour different service areas are shifted to one of four operaLillg frequPnries, F(1) -S F(4). This corresponds to one of four dirr~lellL center frequency settings for 2nd LO
Source 35.

As shown in Figure 7, each of the SubSC.~ i in service areas 1-4 would receive modulated signals, but each service area I~A~ r bro~lcAet~ the n modulated signals at a dirr~lellL O~ dLillg frequency. As a result, adjacent service area 10 ill~lÇelellce is ~ irlrA"Ily reduced.

In one embodiment of the present invention, opeldlillg frequencies F(1) - F(4) are spaced 130 MHz apart and each of the n mQ~ tP~l signals are spaced wi~ a 10 MHz "guard band" between each band to ensure mininn~l adjacent cell hll~lr~ ce (note: this embodiment A~sllmPs that each of the bands of n modlllAtp-d signals occupies 15 a speclLulll of approximately 120 MHz wide). In another impl~LLlellldlion, the band of n signals are shifted to one of seven operating frequencies.

The output from Mixer 34 of Figure 6iS bAnfllimitP~l by RAn~lpA~ Filter 36 to remove undesired frequency components introduced by the frequency shifting process of the mixer. The frequency of the output of the R~n-lpa~ Filter 36is one-20 half of the final broadcast operating frequency. Driver Amplifier 37iS a sdluLdling~non-linear amplifier aclju~ted to amplify signals in a frequency range that is one-half of the final broadcast O~)eldLUlg frequency. Impl~."~ Afion savings are realized by decreasing the frequency range of the Driver Amplifier 37 to operate at one-half of the final broadcast c~eldLillg frequency.

As described previously, due to the ~ LicLed amplitude variation of a signal - that is mndlllAtP~1 into the SQR-SQSPK format of the present invention, a saturating non-linear amplifier can be used to reliably amplify the SQR-SQSPK mo-llllAte~l signal.

itior~ implementation savings are realized because the SQR-SQPSK m~ 1]~tinn technique does not require a linear driver amplifier be used to m~int~in amplitude characteristics of the modulated system.

After amplification, the frequency of the SQR-SQPSK modulated signal is 5 doubled by Power Amplifier/Doubler 38. Power Amplifier/Doubler 38 is a diode doubler power amplifier which fimcticn~ to double the frequency of its input signal.
As described above, the SQR-SQPSK signal is designed so that when amplified by adiode doubler power amplifier, the resulting signal is a conventional SQPSK signal.
Thus, output signal 39 of Power Amplifier/Doubler 38 is a signal having a frequency 10 equal to the desired broadcast upeld~ g frequency and having a ~;ollv~ ion~1 SQPSK
modulation format.

One aspect of ~e present invention that should be noted is that the SQR-SQPSK modulated signal is b~n-llimit~d in frequency by R~nrlpac~ Filter 36 before being amplified by the Power Amplifier/Doubler 38 and this b~n~11imit;ng is preserved l5 at the oulput of Power Amplifier/Doubler 38. In contrast, prior art methods using conventional QPSK mo~ln1~tinn and non-linear amplification t~o~hni~ es requires b~n-l1imiting before and after the amplification step due to the non-linear amplifier's intolerance to amplitude variations OC~ l~llg in a QPSK-formatted signal. The ability of the present invention to only b~nrllimit once before the amplification stage allows 20 for a more ~rri~;iell~ usage of power, since an additional b~nri1imiting step after amp1ifi~~~tion ~at reduces the effective ~ l power of conventional QPSK-formatted signals can be omitted..

Pigures 8A-D and 9A-D are graphs illustrating ban.l1imiting and amplification advantages of the SQR-SQSPK modulation tPrhni~le of the present invention (Figures 2~ 9A-D~ over the prior art collv~llLional QPSK modulation technique (Figures 8A-D).
Figures 8A and 9A illustrate ~e power :,pe.;~lulll of a QPSK and SQR-SQSPK
r~,l,l,al~d signal, respectively, before b~nfl1imiting and amplifying with a power amplifier, Figures 8B and 9B illustrate ~e power spectrum of ~e QPSK and SQR-SQSPK ~ln,dl~d signals, respectively, after b~n~l1imiting and amp1ifir~ti--n by a ~ CA 02236088 1998-04-29 ~ IU S 9 6 / 1 8 8 0 ~
~PEA/llS 1 3 J UN 199 /

doubler power amplifier, Figures 8C and 9C illustrate the amplitude vs. time of the QPSK and SQR-SQSPK formatted signals, respectively, after b~n-11imiting, and Figures 8D and 9D illustrate the polar plot of these signals after b~n-~limiting. In comparison, it can be seen that the SQR-SQPSK signal exhibits smaller amplitude 5 variations in Figures 9C and 9D and a narrower power spectrum in Figure 9B
compared to the amplitude variations and power spectrum of the conventional QPSKsignal as illustrated in Figures 8B, 8C, and 8D. Figure 9C also illustrates that the SQR-SQPSK signal of the present invention does not require additional b~n-ilimitin~
after the amplification performed by the doubler power amplifier, whereas Figure 8C
10 illustrates that the conventional staggered QPSK signal could require an additional . . , b~n-llimiting step.

After modulation and amplification these signals are broadcast to subscribers by antennas located in each service area. Pairs of IF Modulator Segments 20 and RF
Power Segments 21 each generate one modulated and amplified signal 39 within each 15 service area. Each set of signals 39 are coupled to the antenna of the present invention Cc~ Jlisillg independent sector antenna panels. It should be understood that in one embodiment the number of signals 39 ~,elleldle~diS equal to the same number of antenna panels such that each antenna panel broadcasts an independent signal. In another embodiment, some of the panels may broadcast the same signal.

One embodirnent of the antenna of the present invention is a mllltif~e~
polygonal shaped cylinder where each of the faces of the cylinder constitute onedistinct sector antenna panel. Figure 10A illustrates a top view of one embodiment Of zlnt~nnzl 42 of the present invention having eight sector antenna panels 43. Sector ~nt~nn~ panels in this embodiment produce a beamwidth 45' in ~7iml-th (Figure 10B).
In an alternate embodiment, antenna 42 comprises a six-sided polygonal where each face produces a beamwidth of 60- in ~7imnth It should be noted that the RF of each sector signal is identical to the RF of the other sector signals radiated from each tr~n~mitter site antenna. Because each sector antenna is physically separated from the other sector antennas, these sector AMEN~ Sl~EEr W O 97/18674 PCTnJS96/18804 ~nt~nn~c tend to operate as phased arrays when they lldl~7~ signals. The theory of phased array antenna systems predicts that the signals emitted by the individual array antennas will destructively combine with one another at certain pointing angles from the phased array. Conceqnently, there will be directions ext.on-ling ~u~w~d from the S phased array along which no signal energy can be Leceiv~d. In the present invention, the most vulnerable locations for these destructive hll~;lfele~lce zones are found along the ~7imnth~1 boundaries of the wedge-shaped sectors (in~ t~d by 44, Figure l0).Thus to prevent this de~ uclive hlL~lrelellce between sector signals at subscriber locations along the boundaries of the ~7imllth~1 sectors, the antenna polarities of l0 adjacent sectors are of opposite polarities. Therefore, the RF signals from the two sector antennas cannot combine destructively, and the subscriber ~nt~nn~ will receive only one of the two possible sector signals thereby p l~ve~l~hlg de.,L~u~,live hl~lr~lence from OC~;ullillg along the ~7imllth lines ext~-n-ling out from the L~ l antenna where the 45 or 60- wide beams overlap.

I5 The use of independent polarizations for the adjacent sector ~ in the present invention differs from the prior art in that the prior art uses differing antenna polarizations to prevent ullwdll~d and unrelated signals from entering the receiver ~nt(~nn~ In the current invention, however, differing polari_ations are used to prevent similar signals from canceling one another as they impinge simlllt~n~ously upon the 20 receiver antenna.

Figure l l illustrates an array of service areas 45 resulting from the sectorized ion method of the present invention employing an octagonal antenna configuration. As shown, L~ sites 46 reside in the center of each of the service areas 45. Each service area, as described above, broadcasts at one of a set of 25 (lpeldLillg freqll~n~if c thereby reducing destructive hlL~lr~;lel~e between adjacent service areas. In ~ lition~ each service area is se~;L~liGed, such that adjacent sectors broadcast opposite polarity signals as shown in Figure lO. Consequently, the present invention not only reduces illl~l r~ nce along service area boundaries, but also reduces iu~lrl;lellce along sector boundaries within the service area.

It should be noted that the mnltif~red antenna of the present invention also holds the advantage of potential power and implementation savings. In particular, if antenna panels are facing large obstructions (i.e. mountains) such that it is not - nrce~ry or desired to broadcast a signal in that direction, the 5 modulator/amplifier/~ntenn~ panel(s) facing in the direction of the obstruction can be disabled or elimin~trd altogether. Thus, the sectorized antenna can be customized to meet the physical broadcast re4ui.c;lllellL~ of the area while reducing power consumption and impl~m~nt~ti- n cost.

Receiver sub~y~ l 12, shown in Figure 2, includes a RF Dem---lnl~tor Segment 47 and a Settop Box Segment 49. The RF Demo~ tr~r Segment 47 receives a broadcast signal 41 with the particular polarity that the receivillg antenna is designed to accept. The RF Demo~ tor Segment 47 ~lemc)~ tF~s the broadcast signal 41 to recover the underlying digital datastream. The Demo~nl~tor Segmrnt 41 selects one of tbe rh~nnpls encoded in the recovered bil~ l in response to a control 15 signal provided by the subscriber. This control signal ~from the Settop Box Segmrnt 49 is the Channel Select Control 64 and is se!~oct~l by the user through a remote control device or other input device. The selected digital signal charmel 48is sent to the Settop Box Segmrnt49 which decodes the selected channel 48 and puts it into a format suitable for the I/O device that it is co~ ecl~d to.

For in~t~nre, if the settop box is connected to an analog television set, the settop box first dec~,l..~resses the digital video signal and then converts the digital datastream back into an analog television signal which can be displayed by the analog television set.

Figure 12A illustrates one implementation of RF Demodnl~trJr Segment 47 of 25 the present invention and Figure 12B illustrates the embodiment of the Settop Box Segment 49 of the present invention, however it should be understood that the system and method of the present invention is not limited to these impl~ ons.

Referring to Figure 12A, Antenna 50 receives one of broadcast signals 41 W O 97/18674 . PCT~US96/18804 (Figure 2) from Tl;.n~ Subsystem 11. Signal 41 is filtered by a Bandpass Filter 51 to limit the amount of received signal energy to the desired frequency bandwidth.
The Low Noise Arnplifier (LNA) is an amplifier ~esi~nP-i to boost the received signal without adding signifir~nt1y to the level of noise in the signal. The output of the LNA
S and R~nclp~c~ Filter 51 is connected to a Mixer 52, which translates the center frequency of the received signal to an Intermediate Frequency (IF). Signal 53 is then passed through the IF R~n~lp~ Filter 54, which is designed to pass the desired frequency band centered at the IF frequency and reject any other frequency signals.

The demodulator portion of Figure 12A demodulates the output signal 55 of 10 IF R~nrlp~s Filter 54. The particular demodulator impl,o-mPnt~tion shown is a SQPSK
demodulator having in-phase component I and a quadrature-phase component Q
modulation paths. The I dem~ tion path includes Mixer 56 and Threshold Detector 57. The Q demo~ tto}l path includes Mixer 58 and Threshold Detector 59. The demodulator uses a fee~lh~rk path which includes the Carrier Tracking Circuitry 60 15 to op~ ~e the demodulator output. The output of the Carrier Tracking Circuitry 60 controls the frequency of the 2nd Lo. The output from Mixers 56 and 58 are two analog baseband da~LI~tulls. These signals are then processed through Threshold De~;lurs 57 and 59, respectively. The threshold d~lec~ul~ convert the two analogbaseband d~ edllls into binary datastreams which are input into the Digital 20 Datastream Recovery Unity 61. The binary d~ lls are labeled 'I' and 'Q' inFigure 12A, corresponding to an In-phase ~I) and Quadrature-phase (Q) component.
Digital Dalh~ Recovery Unit 61 recovers a clock signal equal to the original tr~n~mitt~l symbol clock rate. It is well known in the art of c~ lir~tions design that in order to accurately ascertain the original information signal from a 25 Ll,.n~ l modulated signal it is nrreS~ry to obtain a symbol clock signal that is equal to the Ll,...xl~ tl symbol rate.

Within the Digital Datastrearn Recovery Unit 61, the I and Q inputs are re-sampled to be aligned with the recovered clock signal and combined to form a single high-speed bil~l~edlll. In order to obtain the data associated with an individual WO 97/18674 PCTAUS96/~8804 channel, the signal must be ~llomllltiplexed. The ~lemllltil)lexing process reverses the procedure depicted in the Time Division Multiplexer 18 of Figure 3. The high-speed biL~ l output 19 from the Time Division Multiplexer 18 of Figure 3 consists of many independent channels. De-multiplexing describes a procedure that allows oneS of the independent channels present in the high-speed bi~Llcalll output 19 to be ~epala~d from the high-speed biL~llealll for subsequent processing. The output of the Digital Dala~ Recovery Unit 61 is Clock 61 and Data 48 signals that are routed to the Settop Box Segment 49.

In the implem~ont~tir~n shown in Figure 12B, the Settop Box Segment 49 is 10 adapted for processing only television channel signals. Thus, it should be understood that similar settop box designs can be adapted to process other types of channelinformation such as digital data for co~ uLt~l systems, video conferencing data, etc.
Rerellillg to Figure 12B, the selected channel data 48 from RF Demodulator Segment 47 is routed to a television settop box. The settop box includes Receiver 65, Video 15 Colll~iession Decoder 66, Analog Video G~llvell~l, Analog Audio Collvel~ 67, Remote Control 68, IR 3~eceiver 69, Settop Host Controller 70, and RS-422 Tr~ncmitter 71. RS-422 Receiver 65 receives the signal from RF Demo~ t r Segment 47 and connects it to Video C~ les~ion Decoder 66. The Video Compression Decoder 66 decolll~lesses the digital, audio, and video signal into the 20 corresponding separate audio and video portions of the selected channel signal. The decolll~less~d audio and video digital television signals are then each reconverted into analog audio and video television signals by Converters 67 and then coupled to the television set. A Remote Control Device 68 provides channel select control signals via IR signals to the television set and also to the settop box to indicate the selected 25 channel. IR Receiver 69 receives the channel select control signals and 11 ansllli~ these to Dem~ tor Segment 47 through Settop Host Controller 70 and Receiver 71.

Due to the efficient spectrum usage of the present invention the system of the present invention is particularly adaptable to a two-way tr~n~mi~ n implem~nt~tion which in~ ln-1~s a wireless signal path from the receiver subsystem 12 to the tr~n~mitter 30 ~ub~ys~lll 11, (commonly referred to as the b~f-k~ l). Back~h~nn~l signals are WO 97/18674 PCT~US96/18804 tr~ncmit~ l at a nc~min~1 carrier frequency that is approxim~tPly the same as the rOl w~Ld channel RF broadcast frequency. The data contained in the backch~nn~l can be Pay-Per-View request data, video data images for video-col~e~ellcillg, distance learr~ing programs, or other types of digital data streams. These backcharmel signals 5 may be in digital or analog format.

In one embodiment of the present invention the backch~nn~l signal is folll.dLL~dinto a hybrid FDM/TDMA (frequency division multiplex/tirne division multiple access) formatted signal. Data is sent from the subscriber in segments - each segment being ~c~i~;n~l to a specific ~ubsclibel. The segm~-ntc are ~csi~n~d a frequency channel and 10 a time slot for tr~ncmicsion within that frequency channel. These ~csignmpnts are unique to the subscriber and insure that the ~ubsclil)er will be the only user of that frequency channel and time-slot pair while the subscriber requires the use of the back~h~nn~ n~k.

Time slots are allocated dyn~mir~lly to the subscribers on a demand basis.
15 Multiple slots may be allocated to a single subscriber to increase the b~krh~nn~?l data rate for a particular subs~liber. The modulation format of the backc1~ l is the same format as fulwald channel signal. In one embodiment of the present invention, the modulation rate of each of the backch~nn~?l FDM carriers is 2.048 Mbps, and the frequency bandwidth occupied by each FDM carrier is approximately 2 MHz. ~urther20 to this embodiment, data is sent from the subsclibel in 64-kbps2 segments and each FDM carrier contains thirty-two 64-kbps TDMA slots.

The back channel carrier frequency is tr~ncmitt~-l at a carrier frequency suf~lciently sepal~d from the forward channel broadcast frequency to prevent mutual h~ rt:~cllce bet~,veen the ful w~rd channel transmission and the b~r~rh~nn 25 L~ c~;c~ion. Figure 13 illustrates an example of spectrum allocation for the forward and backcharmel bands for a given sector in the case where 480 MHz of spectrum is available. As shown, 160 MHz is allocated for the forward channel which, as described above in the one-way imp1P.~ n of the present invention, is enough to accommodate the standard 96 channels. Assuming a guard band of 20 MHz between W O 97/18674 PCTrUS96/18804 the forward channel and b~rkrh~nn~l~ 300 M~Iz remains for b~ h~ l use. As a result, there could exist lS0 FDM carriers (i.e. 300 MHz/2 MHz bandwidth per FDMcarrier) available for the barkrh~nnf l of a given sector (~xsllming 2 MHz per FDM
carrier). In the case in which thirty-two 64 kbps TDMA time slots are present oneach FDM carrier, 4,800 (i.e. 32 slots x lS0 carriers) individual data links per sector can potentially be supported.

In this embodiment, a single FDM carrier can be reserved for use as the control channel for reqllesting b~r~-h~"~f~l frequency channels and tirne slot aSsignm~ntx. The subscriber equipment can initiate a request for a b~rkrh~nn--l by sending a packet to the ll,.nx~ P-r sub~y~Lcl~l l l in one of the control channel time slots. The tr:~nxmitt~-r :iUb:iy:ilc~ ceives this information and sends a frequency channel and time slot assignment to the subscriber. This hlro~llalion from the l sub;!iy:~lclll 11 is sent in an ATM cell broadcast to all subscribers within that base station's sector.

The backrh~nn.-l takes advantage of the inherent syn~hrolli~alion of all subscribers to a clock rate origin~ting from the same source (i.e. Ilanx~ . subsystem 11). This allows for a very accurate tirne ~yllchl-ol~d~ion capability at each subscriber unit. Simple c~lmm~n.1~ sent in the forward channel can be used to correct for differences in the time of arrival of b~rkrh~nn-ol signals received at the L1An~ f-1 subsystem l l . These dirrc-cllces in time of arrival are caused by the variations in propagation path .1iet~nres from each of the subscribers to the given L.;.~ r subsystem site.

It should be understood that the physical implementation of a two-way lld.~"~iccion embodiment of the present invention includes subscriber site Ci~CuiLIy for 25 fo,~l;.)g the back.-h~"Pl signals into the hybrid FDM/TDMA format as well as ~ cilcuiLIy for placing the formatted backrh~nn~ol signals into condition for wireless Ll;."~ icxion to L.~"~",il~r SUbSySL~Ill 11 such as mo~ ti.~n cir~;uiLly for mo~ ting ~e Ç~J... al~ d b~rl~. h~ Pl signals onto an RF carrier signal. Furthermore, thetr~nxmitt~r subsy~L~lll ll in the two-way impl~m~-nt~tinn of the present invention W O 97/18674 PCT~US96/18804 includes an ~ntPnn~ for leceivhlg backrh~nn~l signals within the Ll,.-,x ~ lrr subsystem's service area. The back channels, once received at the ~
sub~.ysL~lll site, are either tr~ncmi1t~d to other subscribers in the service area or back to the provider sub..y~.L~lll depending on the type of back~h~nnPl data being S tr~n~mittfd ~or in~t~nre, in the case of video-col~elellcillg data the tr~n~mitt~r sub..y~ l includes a ~wiL~hing n~Lwolh for routing video-c~ rt;lt;ncillg data between two subscriber sites. In the case in which back channel data is a Pay-Per-View request control signal, Lla~ l 11 Lla1LS111iL~. this data back to the provider subsystem 10.

Although the elements of the present invention have been described in conjunction with certain emborlimP-nts, it is ~pl eiaL~d that the invention can be implemented in a variety of other ways. Con~eqll~ontly, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intPn-led to be considered limiting. Reference to the details of these embo~imPnt~ is 15 not intPnf1Pd to limit the scope of the claims which themselves recite only those Ç~aLult;s regarded as essenti~l to the invention.

Claims

We Claim:

1) In a wireless transmission system including a provider subsystem for providing a plurality of channels of signals, a transmission subsystem for transmitting channels of modulated signals in a wireless manner to a plurality of service areas, and a receiving subsystem for receiving said modulated channel signals, said transmission system comprising:
a means for generating from said plurality of channels a plurality of continuousmodulated signals which are independent of each other, each of said independent signals representing a selectible combination of said plurality of channels, and for providing said plurality of independent signals to each of a plurality of antennas;
each of said antennas including a plurality of individual antenna sections, wherein each of said antenna sections transmits one of said independent signals whereby said independent signals are sectorially transmitted from each antenna.

2) The transmission system as described in Claim 1 wherein each of said independent signals represents different selectable combinations of said plurality of channels of signals.

3) The transmission system as described in Claim 1 wherein at least two of said independent signals represents the same selectable combinations of plurality of channel of signals.

4) The transmission system as described in Claims 2 or 3 wherein said individual antenna sections are arranged in a multifaced polygonal cylindrical configuration.

5) The transmission system as described in Claim 4 wherein said each antenna section has an associated transmission polarity and adjacent antenna sections have opposite associated transmission polarities.

6) The transmission system as described in Claim 5 wherein said multi-faced polygonal cylindrical configuration includes six of said antenna sections and wherein said each section transmits a 60° azimuth of said signal.

7) The transmission system as described in Claim 5 wherein said multi-faced polygonal cylindrical configuration includes eight of said antenna sections and wherein said each section transmits a 45° azimuth of said signal.

8) The transmission system as described in Claim 7 wherein said antenna sections are horn-type antennas.

9) The transmission system as described in Claim 7 wherein said antenna sections are disk-type antennas.

10) In a wireless transmission system including a provider subsystem for providing a plurality of channels of signals, a transmission subsystem including a plurality of antennas for transmitting channels of modulated signals in a wireless manner to a plurality of service areas, and a receiving subsystem for receiving said modulated channel signals, each of said antennas having an associated service area, a method comprising the steps of:
generating from said plurality of channels a plurality of continuous modulated signals which are independent of each other, each of said independent signals representing a selectable combination of said plurality of channels, and for providing said plurality of independent signals to each of a plurality of antennas;
providing said plurality of independent signals to each of a plurality of transmitting means, wherein each transmitting means has an associated service area;
transmitting said independent signals to each service area associated with said each transmitting means wherein said each service area is divided into sectors and each of said independent signals is transmitted to one corresponding sector.

11) The method as described in Claim 10 wherein each of said independent signals represents different selectable combinations of said plurality of channels of signals.

12) The method as described in Claim 10 wherein at least two of said independent signals represent the same selectable combinations of said plurality of channels of signals.

13) The method as described in Claims 11 or 12 wherein said plurality of independent signals are transmitted such that adjacent sectors receive opposite polarity signals.

14) The method as described in Claim 13 wherein each of said plurality of independent signals is a 60° azimuth signal.

15) The method as described in Claim 13 wherein each of said plurality of independent signals is a 45° azimuth signal.

16) A wireless transmission system comprising:
a provider subsystem for converting a plurality of channels of signals into a plurality of formatted independent digital datastreams, each of said formatted digital datastreams representing a selectable combination of said plurality of channels;
a transmitter subsystem including a plurality of transmission means each having an associated service area, said each transmission means modulating each of saidformatted digital datastreams into a corresponding modulated signal so as to generate a plurality of modulated signals which are independent of each other, said each service area being divided into a plurality of sectors and said each transmitter means transmitting each of said independent signals to one corresponding sector within its associated service area;
a receiver subsystem including a plurality of receiver means in each sector within each service area for converting one of said independent modulated signals into its corresponding formatted digital datastream and selecting one channel of signals of said portion of plurality of channels from said corresponding formatted digital datastream.

17) The system as described in Claim 16 wherein each of said independent formatted digital datastreams represents different selectable combinations of said plurality of channels of signals.

18) The transmission system as described in Claim 16 wherein at least two of said independent formatted digital datastreams represents the same selectablecombinations of said plurality of channels of signals.

19) The system as described in Claim 17 or 18 wherein said provider subsystem comprises a plurality of means for generating said each formatted digital datastream, each of said means for generating each of said digital datastreams including means for encoding said plurality of channels into a plurality of intermediate digital datastreams and means for formatting and multiplexing said plurality of intermediate digital datastreams into said each formatted digital datastream.

20) The system as described in Claim 19 wherein said means for formatting and multiplexing formats said formatted digital datastreams into a single ATM
formatted digital datastream.

21) The system as described in Claim 20 wherein said each transmitter means transmits said modulated signals at one of a set of operating frequencies.

22) The system as described in Claim 21 wherein said plurality of channels of signals includes previously compressed digital television signals.

23) The system as described in Claim 22 wherein said plurality of channels of signals also includes digital computer system signals.

24) The system as described in Claim 23 wherein said receiver subsystem further includes a means for converting said selected one channel of signals into a corresponding channel of analog signals.

25) The system as described in Claim 24 wherein said encoding means formats said intermediate digital datastreams according to SONET STS-3 formatting.

26) The system as described in Claim 25 wherein said formatting and multiplexing means performs frequency division multiplexing.

27) The system as described in Claim 26 wherein said a means for encoding comprises an analog-to-digital converter and a means for compressing digital signals.

28) The system as described in Claim 27 wherein said means for compressing uses an MPEG-2 compression format.

29) The system as described in Claim 28 wherein said each transmitter means includes an antenna for transmitting said independent modulated signals, each antenna having a plurality of individual antenna sections for transmitting one of said independent signals and each section having an associated transmission polarity,wherein adjacent antenna sections have opposite associated transmission polarities.

30) The system as described in Claim 29 wherein said receiver means further comprises a receiving antenna for receiving said one independent modulated signal wherein each of said receiver means is tuned to receive said one independent modulated signal having its associated transmission polarity.

31) The system as described in Claim 30 wherein said a means for converting said selected one channel of signals into said corresponding channel of analog signals further including a means for decompressing said selected one channel of signals and a digital-to-analog signal converting for converting said decompressed selected channel of signals into said corresponding channel of analog signals.

32) The system as described in Claim 31 wherein said individual antenna sections are arranged in a multifaced polygonal cylindrical configuration.

33) The system as described in Claim 32 wherein said each receiver means further includes means for transmitting RF signals and said each transmission means further includes means for receiving said RF signals from said receiver means so as to enable two-way transmission between said transmitter subsystem and said receiver subsystem.

34) In a wireless transmission system, a method for transmitting and receiving signals comprising the steps of:
converting a plurality of channels of signals into a plurality of formatted digital datastreams, each of said formatted digital datastreams representing a selectable combination of said plurality of channels;
modulating each of said formatted digital datastreams to generate a corresponding modulated signal thereby generating a plurality of modulated signals which are independent of each other;
providing said plurality of independent signals to each of a plurality of transmitting means, wherein each transmitting means has an associated service area;
transmitting said independent signals to each service area associated with said each transmitting means, wherein said each service area is divided into a plurality of sectors and each sector receives one of said independent signals;
receiving said one independent signal; and converting said one independent signal into a signal usable by a given I/O
device.

35) The method as described in Claim 34 wherein each of said independent formatted digital datastreams represents different selectable combinations of said plurality of channels of signals.

36) The method as described in Claim 35 wherein at least two of said independent formatted digital datastreams represents the same selectable combinations of said plurality of channels of signals.

37) The method as described in Claim 35 or 36 wherein said step of converting a plurality of channels of signals into a plurality of independent formatted digital datastreams, further comprises the steps of multiplexing said portion of said channels into an intermediate digital datastream and means for formatting said intermediate digital datastream into said each formatted digital datastream.

38) The method as described in Claim 37 further including the step of formatting said plurality of formatted digital datastreams into a single formatted digital datastream representing said plurality of formatted digital datastreams, wherein said single digital datastream is reconstructed into said plurality of formatted digital datastreams prior to said modulation step.

39) The method as described in Claim 38 said independent modulated signals are transmitted at one of a set of operating frequencies.

40) The method as described in Claim 38 wherein said each independent datastream is modulated into a square root staggered QPSK (SQR-SQPSK) formatted modulated signal.

41) The method as described in Claim 40 further including the steps of amplifying said modulated signal with a non-linear saturating amplifier and a doubler power amplifier to generating a staggered QPSK modulated signal before the step of transmitting said modulated signals to said service area.

42) In a communication system in which a digital signal is modulated into a conventional staggered QPSK (SQPSK) formatted signal and said SQPSK signal hasassociated amplitude variations, a modulation and amplification method comprising the steps of:
modulating said digital signal to generate a modulated signal having amplitude variations less than said conventional SQPSK formatted signal;
amplifying said modulated signal with a saturating non-linear amplifier.

43) The method as described in Claim 42 wherein said step of modulating restricts phase changes to +45° 0°, and -45° when said modulated signal changes logic states.

44) The method as described in Claim 43 wherein said step of modulating generates a SQR-SQPSK formatted signal.

45) The method as described in Claim 44 wherein when said SQR-SQPSK
formatted signal is amplified by a doubler power amplifier said conventional SQPSK
signal is generated.